Board Thread:General Discussion/@comment-26222858-20150917141812/@comment-6769189-20151003054959

So what if that was his first activation? The DT was the same as when he uses Rebellion, which means he was drawing power from it. It's the same reason why DT stays active even during techniques like Sword Pierce or Round Trip.

Evidenced by Nero, one needs to have ownership of an awakened Devil Arm before they can DT with it.

Almost no matter how you look at it, DT can't be activated without a Devil Arm, not necessarily one in hand, but within the general vicinity and under the users ownership.